The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 11-235467, filed Aug. 23, 1999.
1. Field of the Invention
The present invention relates to an information generating apparatus and a navigation apparatus, or more specifically, a car navigation apparatus that utilizes position information provided through beacons.
2. Description of the Related Art
There are car navigation apparatuses in the prior art with multiple functions such as a function of displaying a road map around the current vehicle position, a function of calculating a recommended route from the start point to the destination and a function of providing route guidance based upon the calculated recommended route. In such a car navigation apparatus, the current position of the vehicle must be detected. For this purpose, it is provided with a bearing sensor that detects the bearing along which the vehicle is advancing, a vehicle speed sensor that detects the vehicle speed and a GPS sensor that detects GPS signals transmitted from a GPS (Global Positioning System) satellite and the like.
In addition, the vehicle traffic information communication system (VICS, operated in Japan) provides road traffic information such as traffic jam information through FM multiplex broadcast, light beacons, radio wave beacons and the like. Information transmitted through light beacons and radio wave beacons includes position information indicating the position at which the beacon device is installed in addition to the VICS information. As a result, such beacon position information can also be utilized to detect the current position of the vehicle.
However, since erroneous position information is sometimes transmitted as the beacon position information, it is not used very often due to the lack of reliability. If the beacon position information can be utilized while assuring a high degree of reliability, it will be extremely useful for navigating a vehicle at a position where no map-matching achieved.
An object of the present invention is to provide an information generating apparatus that utilizes information with improved reliability achieved by improving the re liability of information having low reliability and, more specifically, to provide a navigation apparatus that utilizes position information with improved reliability by improving the reliability of information having low reliability. Another object of the present invention is to provide a car navigation apparatus capable of utilizing position information transmitted through light beacons or radio wave beacons in a highly reliable manner.
In order to attain the above object, a navigation apparatus according to the present invention comprises: a first position information generating device that generates first position information as current position information regarding the navigation apparatus based upon a signal received from outside; a second position information generating device that generates second position information as current position information based upon another signal received from outside; and a control device that implements control to provide route guidance based upon current position information and map information. And the control device uses the first position information as effective current position information if a position corresponding to the first position information generated by the first position information generating device is within an error range set for a position corresponding to the second position information generated by the second position information generating device.
In this navigation apparatus, it is preferred that the first position information has a higher degree of accuracy and a lower degree of reliability than the second position information;
Also, it is preferred that the navigation apparatus is a navigation apparatus installed in a vehicle; and the first position information generating device includes a beacon reception device that receives information transmitted by a beacon device installed at a road and generates the first position information by receiving position information indicating a position at which the beacon device is installed. In this case, it is preferred that the second position information generating device includes a satellite signal reception device that receives position signals from satellites and generates the second position information based upon the position signals which have been received.
Also, it is preferred that the second position information generating device includes a satellite signal reception device that receives position signals from satellites and generates the second position information based upon the position signals which have been received.
Also, it is preferred that a movement detection device that detects movement of the navigation apparatus is further provided, the movement detection device detects the movement of the navigation apparatus occurring over a period of time in elapsing between a time point at which the second position information generating device generates the second position information and a time point at which the first position information generating device generates the first position information, and the control device assumes a new position by incorporating the movement detected by the movement detection device into the position corresponding to the second position information and utilizes the first position information as effective current position information if the position corresponding to the first position information is within the error range relative to the new position.
Also, it is preferred that a movement detection device that detects movement of the navigation apparatus is further provided, the movement detection device detects the movement of the navigation apparatus occurring over a period of time in elapsing between a time point at which the second position information generating device generates the second position information and a time point at which the first position information generating device generates the first position information, and the control device expands the error range set for the position corresponding to the second position information by taking into consideration a traveled distance based upon the movement detected by the movement detection device.
Also, it is preferred that the control device expands the error range set for the position corresponding to the second position information by taking into consideration a length of time elapsing between a time point at which the second position information is generated by the second position information generating device and a time point at which the first position information is generated by the first position information generating device.
Also, it is preferred that the first position information generating device includes a position signal reception device that receives information transmitted by a position signal providing device and generates the first position information by receiving position information indicating a position at which the position signal providing device is installed.
An information generating apparatus according to the present invention, comprises: a first information generating device that generates first information as specific information; a second information generating device that generates second information as the specific information; a control device that uses the first information or the second information as the specific information under different circumstances. And the second information has a predetermined error range with respect to the specific information; the first information has a higher degree of accuracy and a lower degree of reliability than the second information; and the control device uses the first information as the specific information when the first information is within the error range of the second information.
A recording medium according to the present invention records a control program for a navigation apparatus. The control program comprises: a first instruction that generates first position information as current position information regarding the navigation apparatus based upon a signal received from outside; a second instruction that generates second position information as current position information based upon another signal received from outside; a third instruction that determines the first position information as effective current position information if a position corresponding to the first position information generated by the first position information generating device is within an error range set for a position corresponding to the second position information generated by the second position information generating device; and a fourth instruction that implements control to provide route guidance based upon the effective current position information and map information.
A data signal according to the present invention transmitted through a communication line comprises a control program for a navigation apparatus. The control program comprises: a first instruction that generates first position information as current position information regarding the navigation apparatus based upon a signal received from outside; a second instruction that generates second position information as current position information based upon another signal received from outside; a third instruction that determines the first position information as effective current position information if a position corresponding to the first position information generated by the first position information generating device is within an error range set for a position corresponding to the second position information generated by the second position information generating device; and a fourth instruction that implements control to provide route guidance based upon the effective current position information and map information.